This read-only counter tracks the number of ATM cells transmitted on this leaf's VCC, the outbound counterpart to cktLeafAtmInCells. Comparing inbound versus outbound cell counts for a leaf reveals whether traffic flow is roughly symmetric or heavily one-directional, which is expected behavior for some multipoint applications (like one-way video distribution where a leaf might show near-zero cktLeafAtmOutCells) but suspicious for others. An engineer verifying a supposedly bidirectional leaf is actually getting responses back would check that cktLeafAtmOutCells is nonzero and incrementing, not just cktLeafAtmInCells.